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Detailed Load Calculations APPENDIX A Rev. Jan 2011 Application Manual – Liquid Cooled Generator Sets • Effective Surge kW – the Cumulative Peak kW times a multiplier to account for the reduced load effect due to sustained reduced output voltage during the transient surge load. • Effective Surge kVA – the Cumulative Peak kVA times a multiplier to account for the reduced load effect due to sustained reduced output voltage during the transient surge load. The following documents all of the individual load requirements calculations. Load running, starting and peak surge requirements are calculated for each load based on assumed default operating characteristics as displayed on the individual load entry forms. Light Load Calculations Three different light load types can be entered: Fluorescent – A low–pressure mercury type discharge lamp where most of the light is emitted by an excited layer of fluorescent material. The same load characteristics are used for ballast or electronic types. Both are non–linear loads, but GenSize ignores the non–linearity for this load type since this is usually a small part of the total connected load. Incandescent – Standard bulb type lamp assemblies, which use a filament to create light. Discharge (HID) – Lamps that produce light by passing a current through a metal vapor; includes high pressure sodium, metal halide, and mercury vapor discharge lighting. RkW If kVA entered: RkW = kVA x RPF If Ramps entered: 1∅ RkW = (Ramps x voltage x RPF) ÷ 1000 3∅ RkW = (Ramps x voltage x RPF x 1.73) ÷ 1000 RkVA If RkW entered: RkVA = RkW ÷ RPF If Ramps entered: 1∅ RkVA = (Ramps x voltage) ÷ 1000 3∅ RkVA = (Ramps x voltage x 1.73) ÷ 1000 RPF Running power factor as entered or default SkW SkW = RkW for incandescence and florescence SkW = 0.75 x RkW for HID SkVA SkVA = SkW ÷ SPF SPF SPF = RPF, except for HID where default SPF = 0.85 AkW AkW = RkW Ramps 1∅ Ramps = (RkW x 1000) ÷ (voltage x RPF) 3∅ Ramps = (RkW x 1000) ÷ (voltage x RPF x 1.73) Air Conditioner Load Calculations GenSize simply converts tons to horsepower for sizing air conditioning loads at 2 HP/ton as a conservative estimate of the total load for a lower efficiency unit. If you want a more exact size and know the individual component motor loads in the A/C equipment, enter them individually and come up with a demand factor for what loads are likely to start simultaneously. RkW RkW = AC Tons x 2 x 0.746 RkVA RkVA = RkW ÷ RPF RPF Running power factor as entered or default from database SkW High Inertia SkW = SkVA x SPF Low Inertia SkW = SkVA x SPF x 0.6 SkVA SkVA = HP x (LRkVA/HP) x SkVA factor, where LRkVA/HP is the average kVA/HP for the NEMA Code letter of the motor, and SkVA factor is 1.0 for full voltage starting, or from reduced voltage starting table (see Reduced Voltage Starting Method) SPF As entered, or default values from database by HP and starting method For loads that are designated to automatically cycle on and off: A–9
Application Manual – Liquid Cooled Generator Sets PkW PkW = SkW PkVA PkVA = SkVA AkW (non–VFD) AkW = RkW except solid–state starter where AkW = 2.0 x RkW unless a bypass contactor is used, then AkW = RkW AkW (VFD) Conventional AC Inverter: AkW = 2.0 x RkW Pulse Width Modulated: AkW = 1.4 x RkW DC Drive: AkW = 2.0 x RkW Ramps 1∅ Ramps = (HP x 746) ÷ (voltage x Eff. x RPF) 3∅ Ramps = (HP x 746) ÷ (1.73 x voltage x Eff. x RPF) Battery Charger Load Calculations A battery charger is a silicon–controlled rectifier (SCR) assembly used to charge batteries. A battery charger is a non–linear load requiring an oversized alternator. RkW RkW = RkVA x RPF RkVA RkVA = (Output kVA x Recharge Rate) ÷ Efficiency RPF Running power factor as entered or default SkW SkW = RkW SkVA SkVA = RkVA SPF SPF = RPF AkW For 3 pulse, AkW = 2.5 x RkW For 6 pulse, AkW = 1.4 x RkW For 12 pulse, AkW = 1.15 x RkW With input filter, AkW = 1.15 x RkW Ramps 1∅ Ramps = (RkVA x 1000) ÷ voltage 3∅ Ramps = (RkVA x 1000) ÷ (voltage x 1.73) Medical Imaging Load Calculations GenSize calculates a peak voltage dip for when a medical imaging load is operated. This dip must be limited to 10% to protect the quality of the image. If the peak voltage dip is set higher in the project parameters, GenSize will automatically lower it and notify you. The generator set is then sized to limit the voltage dip to 10% when the medical imaging equipment is operated with all other loads running. If multiple medical image loads are used, the peak voltage dip is calculated for the single largest load and assumes only the single largest load will be operated at any one time. Note that GenSize assumes that the medical imaging equipment is not being operated while loads are starting, so the starting voltage dip is calculated separately and is allowed to exceed 10%. RkW If RkVA entered: RkW = RkVA x RPF If Ramps entered: 1∅ RkW = (Ramps x voltage x RPF) ÷ 1000 3∅ RkW = (Ramps x voltage x RPF x 1.73) ÷ 1000 RkVA If Ramps entered: RkVA = RkW ÷ RPF RPF Running power factor as entered or default SkW SkW = RkW SkVA SkVA = SkW ÷ SPF PkW PkW = PkVA x SPF PkVA As entered, or 1∅ PkVA = (Pamps x voltage) ÷ 1000 3∅ PkVA = (Pamps x voltage x 1.73) ÷ 1000 SPF SPF = SkVA ÷ SkW AkW AkW = RkW Ramps 1∅ Ramps = (RkVA x 1000) ÷ voltage 3∅ Ramps = (RkVA x 1000) ÷ (voltage x 1.73) Motor Load Calculations If the motor load is powered by a variable speed or variable frequency drive or is an AC drive on a DC motor, select Variable Frequency Drive (VFD). A VFD is a non–linear load requiring an oversized alternator to match the running load requirements. On the other A–10 APPENDIX A Rev. Jan 2011
Page 1 and 2: Chapter 8 Appendices
Page 3 and 4: Application Manual - Liquid Cooled
Page 9: Application Manual - Liquid Cooled
Page 23 and 24: APPENDIX B CONTENTS APPENDIX B CONT
Page 25 and 26: LINE APPENDIX B 3 2 1 Autotransform
Page 27 and 28: LINE 3 2 1 APPENDIX B MOTOR STARTIN
Page 29 and 30: APPENDIX B FULL-VOLTAGE KVA CURVE k
Page 55 and 56: Application Manual -- Liquid Cooled
Page 57 and 58: Application Manual -- Liquid Cooled
Page 59: Application Manual -- Liquid Cooled

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